Treating textile material with chromium



Patented May 26, 1931 UNITED STATES PATENT OFFICE Y JOHN LEATHAR'I. HAN KEY, OF SALE,- MANCHESTER, ENGLAND TREATING TEXTILE MATERIAL WITH CHROMIUM in, Drawing. Application filed April 4, 1929} Serial no, 352,615, and in Great Britain April so, 1928.

It is well known that it is diflicult to obtain a heavy chromium mordant on cotton. Thus, in a Manual of Dyeing, by Knecht, Rawson & Lowenthal, 7th edition, 1922, p.

8 252, it is pointed out that It is diflicult to impregnate the vegetable fibres with an amount of chromium salt sufiicient to obtain a full shade the demand for a good chromium mordant for the dyeing of cot- 10 ton has notbeencompletely satisfied as yet. Again, in the specification of British Pattent No. 117,715 (1917), page 3, lines 27-28, after reference to the above passage in an 1 earlier edition of Knecht, the following occurs: As there has been no material improvement. in the fixation of chromium mordants since, the problem remains unsolved. The new invention covered by the Patent No. 117,715 which has since lapsed is then described. It involves numerous operations and the fixing of the chromium on the fibre .by relatively strong caustic lyes which, in

actual practice,- is a considerable drawback' Under the term chromium oxide, I include the hydrated forms of chromium oxide usually referred to as chromium hydroxide and which may be represented by the formula Cr O .&:H O, w denoting zero or a positive number.

I have discovered a process whereby chromium may be fixed on the textile fibre efficiently and expeditiously without employment of strong caustic lye. To the best of my knowledge and belief by means of my invention chromium can be fixed on vegetble fibre in larger quantities than have hitherto been possible. On such heavily mordanted fibre very full and deep shades of alizarine and other mordant colours may be dyed- I have further discovered that by fixing on vegetablefibre a large amount of chromium such fibre can be rendered practically fireproof. I do not mention a limit as regards the amount of chromium whichmust be fixed for this purpose. This will vary with the degree of fireproofing required, but as an exa-mpleit may be stated that a cotton fabric having on the fibre fixed chromium equivalent to 28-30% Or (OI-I) .4H O is names highly fireproof. A great advantage of this method of fireproofing'over that depending on the use of soluble bodies such as ammonium sulphate, ammonium phosphate, sodium tungstate, borax, boracic acid'and the like is that the fireproof quality ofkfabric treated by my process is not removedby wetting or washing. Of course, if desired the chromium treatment may be. followed by treatment with a water-soluble fireproofing body or bodies such as those mentioned above. By means of my invention the feel. and handle of cotton fabric can be modified and improved, and other advantages obtained.

My process consists in treatmg textile material with'mixed solutions of a chromate of an alkali metal, preferably sodium chromate, and of a sulphoxylate of an alkali metal,

such as are known in commerce under the Formosul, Rongalite, Britulite, and the like.

I am aware that in. the Principles and Practice of Textile Printing, by Knecht and Fothergill, 1924., p. 213, there is described a process of mordanting calico by means of Hydralite,

sodium bichromate neutralized. with am monia (which I term sodium-ammonium chromate) and formosul and I make no claim to such a process. The sodium-ammonium chromate formosul mixture referred to on which the process depends is unstable and within a short time of mixing say an hour or less, has deposited appreciable quantities of a brown insoluble chromium compound. If filtered off, the deposition begins afresh, and, for this reason alone, the process can possess little practical interest. Material padded with this mixture and aged emerges from the ager a brownish-olive colour, pointing to incompletely reduced chromium compound.

Furthermore, sodium-ammonium chromate is considerably less soluble than is sodium chromate and a saturated solution of sodium-ammoninum vchromate, contains a much'smaller equivalent of chromium in unit volume than does a saturated solution of sodium chromate; consequently the use of this latter solution permits of the blending of a padding liquor with a higher chromium this example.

'chromate solution 60 content than when sodium-ammonium chromate is employed and for this reason it can be caused to deposit a higher percentage of chromium on the fibre.

Again, a highly concentrated sodium-ammoniuin chromate formosul mixture is considerably less stable than a highly concentrated sodium chromate-formosul mixture in spite of the fact that the latter is the richer in chromium. Thus a saturated solution of sodium-ammonium chromate at 18-20? C. possesses the specific gravity of about 60 Twaddell, and is approximately equivalent in chromium content to 24-25 parts sodium bichromate in 100 parts by volume of solution, while a saturated solution of sodium chromate at the same temperature has sp. gr. of about 98 Tw. and is equivalent'in chromium'content to about '60parts of sodium bichromate per 100 parts by volume of solu- 5 cc. of sodium-ammonium Tw. with 10 cc. formosul 60 Tw.,.there is an appreciable evolution of heat the liquor becomes-quickly green and in a out seven hours or less, at ordinary temperature, it will usually have turned into a solid gel of chromium'hydrate.

tion. On mixin Whenquantities of 200-300 cc. are mixed, thischange into gel may be immediate. On the other hand, by mixing 5 and 10 cc. respectively of sodium chromate solution of 98 Tw. and formosul solution of 60 Tw., the temperature risesbut slightly, the solution assumes an olive colour, an if poured onto a filter aper, is yellow. It remains without solidifying into chromium gel for one to three days or more. It is quite easy to mix 200-300 cc. of concentrated sodium chromate and formosul solutions without fear of premature gel formation. It will thus be seen that the process described by Knecht and Fothergill and the process of t is specification are quite distinct. Q

The following example illustrates my inventionywhich, however, is not confined to Solution A Dissolve 600 g. sodiumbichromate in 250 cc. hot water. Add 370 cc. caustic soda lye "7 5 Tw. Dilute the whole with water to one litre.

This givesv a 2022 G.

solution of 98-100 Tw. at

Solution B Dissolve 500 g. formosul in 620 cc. hot water and cool. This gives a solution of about 60 Tw. at 20 C.

To two parts by volume of Solution B gradually add, while stirring, one part by volume of Solution A. (In-bulk work it may be desirable, though not essential to immerse the mixing vessel in cold water to prevent undesirable local rises of temperature.)

egg) colour. Rinse in hot or boiling water and dry. If it is necessary to remove all alkali from the fabric, give a rinse in dilute acetic acid followed by a hot water rinse.-

According to the amount of chromium it is desired to incorporate with the fibre, the process may be repeated two, three or more times; or if less chromium is required on the fabric, a more dilute padding mixture may be used, but in this case it is advisable to increase the relative proportion of formosul.

When the padding and steaming process is to be repeated in order to incorporate additional chromium with the fibre, it is desirable that an acid rinse should be given after the material leaves the ager and instead of following this by a plain water rinse, there may be added to the last water some wetting-out agent, e. g., such as may be obtained by the condensation with hydrocarbons of alcohols as propyl or butyl alcohol followed by sulphonation. The material is dried with the wetting-out liquor adhering. Provided the wetting-out agent is of such a nature as not to form ob ectionable precipitates with the chromium padding liquor, its presence facilitate the penetration of the latter into the material. Another method of facilitat ing penetration during the second padding is to secure that after padding, a eing and rinsing, the material is only about t tee-quarters dried up, that is to say, it leaves the tins or other drying apparatus with a slight amount of moisture left in it. Such procedure, however, is not essential, but merely "a posslble convenience, and after the first padding, ageing and rinsing, the material may be dried up in the usual manner preparatory to further padding, if this is preferred. The padding solution can be made still more stable by the addition of small quantities of caustic soda, glucose or glycerine, either alone or in; admixture, but excess must be avoided or the precipitation and fixation of chromium on the fibre may be hindered or even prevented. Also, lower temperatures than C. may be used in the ager, provided sufiicient time be given and the atmosphere remain sufliciently moist.

It is thou 'ht that the chromium is fixed in a form that may be represented by the formula Cr (OH) AH O. As a ide, it may be stated that a bleached cloth ta en once through the aforementioned paddin mixture and aged as directed retaine chro--- mium on the fibre equivalent to 13.1% Cr (OH) .4H O, which is equivalentto an i equivalent to 28% Cr (OH) .4H O, which increase in wei ht of the original cloth of 15%. When t e operation was repeated twice, making three times in all through the paddmg liquor, the chromium on the fibre was is equivalent to an increase of 39% on the ori mal weight of the fabric.

e process can be applied to cotton, artificial silk, jute, linen, half-wool, natural 10 silk and tussah silk and other fibres, whether as loose material, yarn, cloth, etc. I

What I claim and desire to secure by Letters Patent is 1. The process ofv fixing chromium on textile fibre which consists in treating such fibre with a mixture consisting of a chromate of an alkali metal and a sulphoxylate of an alkali metal, and ageing.

2. The process of fixing chromium on vegetable fibre which consists in treating such fibre with a mixture consisting of a chromate of an alkali metal and a sulphoxylate of an alkali metal, and ageing.

3. The process'of fixing chromium on cotton fibre which consists in treatin such fibre with a mixture consisting of a c romate of an alkali metal and sulphoxylate of an alkali metal, and ageing.

4. The process of fixing chromium on tex- 3 tile fibre which consists in treating such fibre with a mixture consisting of sodium chromate and sodium sulphoxylate, and ageing.

5. The processof fixing chromium on vegetable fibre which consists in treating such fibre with a mixture consisting of a sodium chromate and sodium sulphoxylate, and

ageing.

6. he process of fixing chromium on cotton fibre which-consists in treating such fibre 40 with a mixture consisting of sodium chromate and sodium sulphoxylate, and ageing.

7. The process of fixing chromium on vegetable fibre in quantit suflicient to make it substantially fire-proo which'consists in impregnating it once or more than once with a mixture consisting of solutions of sodium chrolnate of about 100 Twaddell and of commercial sodium sulphoxylate of about 60 Twaddell, and ageing after each impregnation.

In testimony whereof, I aflix my signature.

JOHN LEATHART HANKEY. 

